Win current game:
Press 7, 7, 9, 8, 8, 9, # before game play begins. You will hear a sound if you have entered the code correctly.

Level select:
Press 7, 7, 9, 8, 8, 9, 9 at the map screen.

View programmers' heads:
Press 1, 4, 2, 8, 3, 7, 2, 2 at any level with the three "cheerleader" aliens before game play starts.